Recs.
Updated
Specs
Pros
Pro Easy to learn
The entire Rust ecosystem is known for having excellent, modern documentation, and Ion is no exception. Couple that with it having far less cruft (ie fewer things to learn) some syntactic and conceptual inspiration from Rust, and suddenly you have a very easy to learn (and still very powerful) shell.
Pro Written in Rust
Shells written in C are often riddled with memory-based vulnerabilities that lead to high profile security flaws that are continually discovered decades later. GNU Bash's Shellshock vulnerability, for example, is an example of a vulnerability that Rust prevents. Rust raises the bar for minimum code quality standards by enforcing various restrictions on type/variable usage, and therefore Ion provides a high quality code base from the start.
Pro Method syntax enables a new level of capabilities
Offers a unique concept of string and array methods, whereby invoking the name of a method, and supplying arguments to it, you can perform otherwise complex text manipulation at expansion time. Also supports recursively processing the results of method expansions within method expansions.
Cons
Con Still in development
There's a number of paper cuts that have yet to be addressed. It's been progressing very rapidly though. Some features have yet to be implemented, some logic bugs have yet to be fixed, and it's not been tested much in the wild. Very early in it's life as of 2017.
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Comments
Flagged Pros + Cons
Con Written in Rust
Too much hype around rust. It's just a tongue, not a silver bullet.